JP2016047626A - Rigid reinforcement ring and tire vulcanization method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanization method of a pneumatic tire, which does not reduce a design freedom degree and productivity, while enhancing dimensional accuracy of a pneumatic tire.SOLUTION: A vulcanization method is characterized in that: a green tire T is set in a mold 1; a bladder 2 is inserted into inside of the green tire T for inflating the bladder 2, thereby the green tire is pressed against outside of a tire radial direction for vulcanization molding. The bladder 2 is inflated in a state that, a rigid reinforcement ring 3 is interposed between an inner peripheral face of a region corresponding to a tread part of the green tire T, and an outer peripheral face of a region corresponding to a tread part of the bladder 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an annular member used for vulcanization molding of a pneumatic tire and a tire vulcanization method using the same.

  As a method of vulcanizing and forming a pneumatic tire, after setting a green tire inside the mold, a vulcanizing bladder is inserted inside the green tire, and steam or the like is injected, filled, and inflated. Tires are often pressurized and heated. However, in vulcanization molding using a vulcanizing bladder, it is possible that the components of the pneumatic tire will flow and not be arranged as designed. In such a case, the desired tire performance may not be exhibited. Moreover, in order to manufacture a high-performance pneumatic tire, it is necessary to further increase the arrangement accuracy of the tire constituent members.

  In order to increase the dimensional accuracy of a pneumatic tire and improve tire performance, a vulcanization method using a rigid core as an inner mold has been proposed (see, for example, Patent Document 1). However, in the vulcanization method using a rigid core, it is difficult to cope with the thermal expansion of the tire during vulcanization, the applicable tire shape is limited, and it is difficult to remove the vulcanized tire from the inner mold In addition to the low productivity, there is a problem that the manufacturing cost becomes high. For this reason, there has been a demand for a method for vulcanizing a pneumatic tire that increases the dimensional accuracy of the pneumatic tire and does not reduce the degree of freedom in design and productivity.

JP 2007-69497 A

  An object of the present invention is to provide a tire vulcanization method in which the dimensional accuracy of a pneumatic tire is increased while the degree of freedom in design and productivity are not reduced.

  The rigidity-enhanced ring of the present invention that achieves the above object is provided in the tread portion of the green tire when a green tire is set in a mold and a bladder is pressed from the inside of the green tire to the outside in the tire radial direction. A cylindrical ring interposed between the inner peripheral surface of the corresponding region and the outer peripheral surface of the region corresponding to the tread portion of the bladder, and the stress required to cause the ring to undergo a predetermined amount of tensile deformation in the circumferential direction. Is greater than the stress required to cause a predetermined amount of compressive deformation in the circumferential direction.

  Further, the tire vulcanization method of the present invention is a tire vulcanization method in which a green tire is set in a mold, a bladder is inserted inside the green tire and inflated to press the tire outward in the tire radial direction. The bladder is inflated with the rigidity reinforcing ring interposed between the inner peripheral surface of the region corresponding to the tread portion of the green tire and the outer peripheral surface of the region corresponding to the tread portion of the bladder. It is characterized by making it.

  According to the rigidity-enhanced ring of the present invention and the tire vulcanizing method using the same, tensile stress in the circumferential direction is compressed between the inner peripheral surface of the tread portion of the green tire and the outer peripheral surface of the tread portion of the bladder. Since a larger reinforced ring is placed and vulcanized, it is possible to limit the outer peripheral diameter of the bladder to swell and limit the shape of the inner peripheral surface of the tire and adjust the thickness in the tire radial direction. it can. Further, since the expansion in the tire radial direction of the bladder is suppressed, the expansion in the tire width direction is increased, so that the thickness of the tire shoulder portion can be reduced. Thereby, the dimensional accuracy of a pneumatic tire can be made high. Furthermore, the design flexibility of the tire can be further increased by appropriately adjusting the outer diameter and width of the rigid reinforcing ring. Moreover, since it is only necessary to use the rigidity-enhanced ring together with the existing bladder, the productivity is maintained and the manufacturing cost is not deteriorated.

  The outer diameter of the rigid reinforcing ring is substantially equal to the inner diameter of the vulcanized tire, the width of the rigid reinforcing ring is preferably substantially equal to the width of the tread portion of the vulcanized tire, and the vulcanized tire and bladder are Separable. Further, the rigid reinforcing ring may be a ring obtained by covering a reinforcing body in which a reinforcing wire having a twisted structure is wound at least in the tire circumferential direction with an unvulcanized rubber and vulcanizing the same. Furthermore, it is preferable that the tensile rigidity in the tire circumferential direction of the rigidity reinforcing ring is larger than the tensile rigidity in the tire circumferential direction of the bladder. This rigid reinforcing ring can achieve deformation other than tensile in the circumferential direction with a weak force, can be easily removed from a vulcanized pneumatic tire, and can be used for repeated vulcanization molding.

  In the tire vulcanizing method of the present invention, a green tire assembly in which green tire components are integrally assembled on the outer periphery of a rigid reinforcing ring can be manufactured, and the green tire assembly can be set in a mold. . A rigid reinforcing ring can be inserted into a lumen of a pre-formed green tire and brought into close contact with it to produce a green tire assembly, and a bladder can be inserted inside thereof. These green tire assemblies may be set inside a mold that can be divided into a plurality of parts.

  The tire vulcanizing method of the present invention can produce a high-quality pneumatic tire stably and at low cost by vulcanizing a green tire using the above-described rigidity-enhanced ring, thereby providing high dimensional accuracy.

It is explanatory drawing which shows typically an example of embodiment of the tire vulcanization method using the rigidity reinforcement ring of this invention in a meridian direction cross section. (A) (b) (c) is explanatory drawing which shows typically an example of embodiment of the rigidity reinforcement ring of this invention, (a) is a perspective view of a rigidity reinforcement ring, (b) is (a). The perspective view which removes and shows a part of surface of the rigid reinforcement ring of FIG. 3, (c) is a perspective view of other embodiment of a rigid reinforcement ring. (A) (b) (c) is explanatory drawing which shows typically opening and closing of the metal mold | die at the time of a vulcanization | cure, (a) vulcanizes | curves when setting a green tire to a metal mold | die. (C) is a sectional view of the tire in the equator direction when the vulcanized tire is taken out. In the Example using the rigidity reinforcement ring of this invention, it is sectional drawing of the expanded bladder at the time of vulcanization | cure. In the comparative example which shows a prior art, it is sectional drawing of the bladder expanded at the time of vulcanization | cure.

  Hereinafter, the rigid reinforcement ring of this invention is demonstrated based on embodiment shown in the figure.

  FIG. 1 is an explanatory view schematically showing a mold 1, a vulcanizing bladder 2 (hereinafter referred to as “blader 2”), and a green tire T during vulcanization molding. FIG. 1 shows a state where the green tire T is pressed against the inner surface of the mold 1 by expanding the bladder 2. The green tire T includes a tread portion T1, a side portion T2, and a bead portion T3.

  In the present invention, the rigidity reinforcing ring 3 is disposed between the inner peripheral surface of the region corresponding to the tread portion T1 of the green tire T and the outer peripheral surface of the region corresponding to the tread portion T1 of the bladder 2. The rigidity reinforcing ring 3 is a cylindrical ring, and it is necessary that the stress required for a predetermined amount of tensile deformation in the circumferential direction is greater than the stress required for a predetermined amount of compressive deformation in the circumferential direction. is there. That is, the rigidity reinforcing ring 3 has a property that it is difficult to extend in the tire circumferential direction and is easily compressed.

  By fitting the rigid reinforcing ring 3 to the outer periphery of the bladder 2, when the bladder 2 expands during vulcanization molding, the rigid reinforcing ring 3 hardly expands in the circumferential direction, and changes in its diameter are suppressed. In particular, the crown portion (tread portion) is restrained from bulging round against the intention, and the outer peripheral shape of the bladder 2 is restricted. That is, by using the rigid reinforcing ring 3, the shape of the inner peripheral surface of the tire when the bladder 2 expands during vulcanization molding is limited, and the thickness in the tire radial direction in the region corresponding to the tread portion is adjusted to achieve dimensional accuracy. Can be high. For this reason, it is preferable that the rigidity reinforcement ring 3 has a tensile rigidity in the tire circumferential direction larger than that of the bladder 2 in the tire circumferential direction.

  Further, since the bladder 2 fitted on the rigidity reinforcing ring 3 is limited in expansion in the tire radial direction, the bladder 2 is easily expanded in the opening of the rigidity reinforcing ring 3, that is, in the tire width direction. As a result, since it is relatively slow to make contact with the inner surface of the mold and it is difficult to sufficiently apply the pressing force, it is sufficient for the shoulder region of the green tire that has been one of the causes of the long vulcanization time. Can be heated and pressurized. That is, by using the rigidity reinforcing ring 3, the thickness of the tire shoulder portion can be reduced to increase the dimensional accuracy, and the vulcanization time can be shortened.

  The rigidity reinforcing ring 3 has a feature that in addition to a large tensile stress in the circumferential direction, a compressive stress in the circumferential direction is small. In the initial stage of tire vulcanization molding, vulcanization of rubber such as carcass and belt layer close to the tire inner surface proceeds, and vulcanization of the entire tire cross section including the inside of the tire proceeds after the next intermediate stage. As the vulcanization of the unvulcanized rubber proceeds, the volume of the rubber increases due to thermal expansion. For this reason, when vulcanization of the entire tire cross section proceeds after the middle stage, the vulcanized rubber close to the tire inner surface where vulcanization has progressed in the initial stage due to thermal expansion, the circumference of the tire lumen shrinks, Deforms radially inward. Therefore, the rigidity-enhanced ring 3 whose circumference has been expanded by the expansion of the bladder 2 in the initial stage of vulcanization molding needs to be reduced in the middle stage and thereafter. Since the rigidity-enhanced ring 3 of the present invention has a small circumferential compressive stress, it can follow the behavior of the vulcanized rubber after the middle stage and can prevent failure such as buckling.

  FIGS. 2A to 2C are explanatory views schematically showing an example of an embodiment of the rigid reinforcing ring 3 of the present invention. As shown in FIG. 2, the rigidity reinforcing ring 3 is a cylindrical ring, and its dimensions are not particularly limited, but its outer diameter is substantially the same as the inner diameter of the vulcanized tire, and the width of the ring is increased. It is preferable that the width of the tread portion of the vulcanized tire is substantially equal. Thereby, the shape inside the radial direction of the area | region corresponded to the tread part of a tire can be adjusted.

  2A illustrates the cylindrical rigid reinforcing ring 3 whose outer diameter is constant in the tire width direction, but the outer diameter of the rigid reinforcing ring 3 is not limited to the illustrated example. For example, when manufacturing a pneumatic tire in which the inner peripheral edge of the tire cross section is linear, the rigid reinforcing ring 3 illustrated in FIG. 2A can be used as it is. On the other hand, when manufacturing a pneumatic tire in which the inner peripheral edge of the tire cross section is designed in an arc shape, the outer diameter of the rigidity reinforcing ring 3 can be changed in the tire width direction along the designed arc. That is, the shape of the rigidity reinforcing ring 3 may be determined according to the cross-sectional shape of the designed tire. Thereby, the design freedom of a tire can be made higher.

  The configuration of the rigid reinforcing ring 3 is not particularly limited as long as the tensile stress in the circumferential direction has a characteristic greater than the compressive stress. As the rigidity reinforcing ring 3, for example, as shown in FIG. 2B, a reinforcing body in which a reinforcing wire 4 having a twisted structure is wound at least in the tire circumferential direction is covered with an unvulcanized rubber 5, and this is added. A sulfurized ring is preferred. By configuring the rigid reinforcing ring 3 with vulcanized rubber made of a reinforced wire having a twisted structure, the tensile stress in the circumferential direction is increased, the compressive stress in the circumferential direction is decreased, and the unvulcanized rubber and the bladder are not bonded. It is good to. Thereby, the mold release property of the vulcanized tire can be improved. The rigid reinforcing ring 3 can be easily peeled off from the inside of the vulcanized tire taken out from the mold 1 and taken out.

  Examples of the reinforcing wire 4 constituting the rigid reinforcing ring 3 include an organic fiber cord and a steel cord. Examples of organic fiber cords include polyester fiber cords, polyamide fiber cords, rayon fiber cords, aramid fiber cords, polyethylene naphthalate fiber cords, polyolefin ketone fiber cords, and acrylic fiber cords. The twisted structure of these fiber cords can be appropriately determined so that predetermined tensile stress and compressive stress can be obtained when the rigid reinforcing ring 3 is used. Further, a reinforcing body is formed by winding the reinforcing wire 4 in a spiral shape in the tire circumferential direction while applying an appropriate tension. The tensile stress in the circumferential direction of the rigid reinforcing ring 3 can be adjusted by the twisted structure of the reinforcing wire 4 and the tension during winding.

  The rigid reinforcing ring 3 is obtained by covering and vulcanizing a reinforcing body made of the above-described reinforcing wire 3 by sandwiching it with a sheet of unvulcanized rubber 5. As a coating method with the unvulcanized rubber 5, the reinforcing wire 3 may be previously coated with the unvulcanized rubber, and this may be spirally wound in the tire circumferential direction.

  Moreover, the rubber component which comprises the rigidity reinforcement ring 3 is not specifically limited, What is necessary is just a rubber component which usually comprises the rubber composition for vulcanization bladders, and the rubber composition for tires. Examples of the rubber component include butyl rubber, silicon rubber, fluorine rubber, natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber.

  The thickness of the rigidity reinforcing ring 3 is not particularly limited, but is preferably 1 to 10 mm, more preferably 2 to 7 mm. If the thickness of the rigid reinforcing ring 3 is less than 1 mm, there is a possibility that the effect of adjusting the shape of the tire inner peripheral surface at the time of vulcanization molding cannot be obtained sufficiently. On the other hand, if the thickness of the rigid reinforcing ring 3 exceeds 10 mm, there is a possibility that the effect of reducing the circumference after the middle stage of vulcanization molding cannot be obtained sufficiently. Further, the optimum thickness of the rigid reinforcing ring 3 is not uniform depending on the shape and size of the tire to be vulcanized.

  In addition, as shown in FIG. 2 (c), the rigidity reinforcing ring 3 can be made thinner at the end in the tire width direction than at the center region, and can be extended from a predetermined position near the end in the width direction. A taper 6 may be provided toward the portion to gradually reduce the thickness. By providing the taper 6 at the end of the rigidity reinforcing ring 3, the shape change of the tire inner peripheral surface at the boundary line of the end of the rigidity reinforcing ring 3 can be moderated.

  Since the rigid reinforcing ring 3 only needs to be used together with the existing bladder 2 and vulcanized and molded, the conventional productivity is maintained and the manufacturing cost is not deteriorated.

  Hereinafter, a method for vulcanizing a pneumatic tire using the rigid reinforcing ring 3 will be described. In the tire vulcanizing method of the present invention, a state in which the above-described rigidity reinforcing ring 3 is interposed between the inner peripheral surface of the region corresponding to the tread portion T1 of the green tire T and the outer peripheral surface of the bladder 2 is the mold 1. It is set inside and vulcanized by expanding the bladder 2. As described above, since the outer periphery of the bladder 2 is fitted with the rigidity reinforcing ring 3, the shape on the tire inner peripheral side is defined by the outer periphery shape of the rigidity reinforcing ring 3, and the pressing of the green tire at the shoulder portion is performed. It can work effectively.

  In the vulcanization method of the present invention, a green tire assembly in which the constituent members of the green tire T are integrally assembled on the outer periphery of the rigidity reinforcing ring 3 is manufactured, and the obtained green tire assembly is set in the mold 1 can do. Thereby, the rigidity reinforcement ring 3 can be reliably arrange | positioned in the internal peripheral surface of the area | region corresponded to the tread part T1 of the green tire T, and the dimensional accuracy of a tire can be made higher.

  As another embodiment, the green tire T is formed in advance by a normal method, and the green tire assembly is manufactured by inserting the rigid reinforcing ring 3 into the lumen of the obtained green tire T. Can be set inside. Thereby, a green tire assembly can be easily manufactured.

  As a metal mold | die which sets the obtained green tire assembly, as shown to Fig.3 (a)-(c), the metal mold | die 1 which can be divided | segmented into plurality can be used preferably. FIGS. 3A, 3B, and 3C are explanatory views schematically showing opening and closing of the mold at the time of vulcanization molding in a sectional view in the equator direction of the tire. 3A is a cross-sectional view of the tire when the green tire is set in a mold, FIG. 3B is a vulcanization, and FIG. 3C is a sectional view of the tire when the vulcanized tire is taken out.

  As illustrated in FIG. 3A, by using a mold 1 that can be divided into a plurality of parts, a green tire assembly having substantially the same diameter as that of the vulcanized tire is set in the mold 1. Easy to do. The number of divisions of such a sectional mold can be determined according to the tire shape and tire size.

  Since the pneumatic tire obtained by the tire vulcanizing method of the present invention has dimensional accuracy close to the designed value, the intended tire performance can be achieved more reliably. For example, a pneumatic tire vulcanized and molded using the cylindrical rigid reinforcing ring illustrated in FIG. 2A prevents the thickness of the tread portion from becoming flat and the central region of the tread portion from being thinned. The thickness can be made substantially uniform. Thereby, the rolling resistance of the pneumatic tire can be further reduced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  When producing a green tire of the same specification (tire size 205 / 55R16), Example 1 was vulcanized using a rigid reinforcing ring, and Comparative Example 1 did not use a rigid reinforcing ring. The rigid reinforcing ring is a polyester fiber cord (corresponding to a total fineness of 2200 dtex and a twist structure of 46 × 46 (double twisted)) spirally wound around the tire in the circumferential direction with 50 ends / 50 mm and covered with butyl rubber. A vulcanized cylindrical ring (diameter 570 mm, thickness 2.3 mm) was used.

  4 and 5 show the results of simulating the cross-sectional form of the bladder expanded during vulcanization molding in Example 1 and Comparative Example 1. FIG. In the cross-sectional form in which the bladder in Example 1 shown in FIG. 4 is expanded, the region corresponding to the tread portion is flat, and the pneumatic tire having a flat tread portion can be vulcanized with a substantially uniform thickness. it can. Furthermore, it is expected that the bladder expands and presses sufficiently to the tire shoulder.

  On the other hand, in the cross-sectional form in which the bladder in Comparative Example 1 shown in FIG. 5 is expanded, the bladder bulges radially outward in a region corresponding to the tread portion. For this reason, when it is going to vulcanize-mold the pneumatic tire which made the tread part flat, we are anxious about the thickness of the center area | region of a tread part becoming thin. Further, it is recognized that the bladder expands to the tire shoulder portion as compared with the first embodiment.

  The tires obtained in Example 1 and Comparative Example 1 were mounted on rims (16 × 6.5 J), respectively, and the air pressure was changed to JISA prescribed air pressure, and applied to an indoor drum tester (drum diameter 1707 mm) in accordance with JIS D4230. Then, the resistance force at a test load of 2.94 kN and a speed of 50 km / hour was measured to obtain rolling resistance. As a result, when the resistance of Comparative Example 1 was 100, the resistance of Example 1 was 90. As a result, it was confirmed that the pneumatic tire vulcanized and molded by the method of Example 1 formed the tread portion in a more flat shape and greatly reduced the rolling resistance.

1 Mold 2 Vulcanized bladder 3 Rigid reinforcement ring 4 Reinforcement wire 5 Unvulcanized rubber 6 Taper T Green tire T1 Tread part T2 Side part T3 Bead part

Claims (9)

  When the green tire is set in a mold and the bladder is pressed from the inside of the green tire to the outside in the tire radial direction and vulcanized and molded, an inner peripheral surface of a region corresponding to the tread portion of the green tire, and the tread of the bladder A cylindrical ring interposed between the outer peripheral surfaces of the region corresponding to the portion, and the stress required to cause a predetermined amount of tensile deformation in the circumferential direction of the ring causes a predetermined amount of compressive deformation in the circumferential direction. The rigidity-enhanced ring is characterized by being larger than the stress required.   The outer diameter of the ring is substantially the same as the inner diameter of the vulcanized tire, the width of the ring is substantially the same as the width of the tread portion of the vulcanized tire, and is separable from the vulcanized tire and bladder. The rigid reinforcing ring according to claim 1, wherein:   The reinforcement of rigidity according to claim 1 or 2, comprising a reinforcing body in which a reinforcing wire having a twisted structure is wound at least in the tire circumferential direction, and is formed by covering the unreinforced rubber with a vulcanized ring. ring.   The rigidity-enhanced ring according to any one of claims 1 to 3, wherein a tensile rigidity in the tire circumferential direction of the ring is larger than a tensile rigidity in the tire circumferential direction of the bladder.   A tire vulcanizing method in which a green tire is set in a mold, a bladder is inserted inside the green tire and inflated to press the tire radially outward to vulcanize the tire, the tread portion of the green tire The bladder is expanded in a state where the rigidity reinforcing ring according to any one of claims 1 to 4 is interposed between an inner peripheral surface of a region corresponding to the outer peripheral surface of a region corresponding to a tread portion of the bladder. A tire vulcanizing method characterized by comprising:   A green tire assembly is produced by integrally assembling the components of the green tire on the outer periphery of the rigid reinforcing ring according to any one of claims 1 to 4, and the green tire assembly is set in the mold. The tire vulcanizing method according to claim 5.   5. The green tire assembly is manufactured by inserting the rigid reinforcing ring according to any one of claims 1 to 4 into a lumen of a pre-formed green tire, and a bladder is inserted therein. The tire vulcanization method described in 1.   The tire vulcanizing method according to claim 6 or 7, wherein the green tire assembly is set inside a mold that can be divided into a plurality of parts.   A pneumatic tire obtained by the tire vulcanizing method according to claim 5.

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